This invention relates to a mechanism for restricting the rotation of a tone arm and raising/lowering the tone arm by which a pickup of the tone arm can be lowered onto a desired position on a record.
When placing the pickup of a tone arm at a desired recorded portion of a record having a plurality of recorded portions on one side thereof, it is required to properly restrict the rotation of the tone arm. Conventionally, for this purpose, a servo motor is employed as a drive source for the tone arm. A photosensor detects the difference in light reflectance between the turntable and the record or a difference in reflectance between recorded and non-recorded portions and the tone arm is restricted in rotation in accordance with a detection signal of the photosensor. However, such prior mechanisms require relatively expensive parts such as servomotors and photosensors, resulting in an increased cost of manufacture. Also, in prior mechanisms, a minute difference in the level of the reflected light is detected, and the tone arm is controlled in accordance with the thus detected signal, resulting in disadvantages such that the mechanism is liable to malfunction and becomes complicated in construction.
Conventionally, there have also been known various mechanisms for raising/lowering tone arms, one of which is arranged such that a drive source for rotating the tone arm in the horizontal direction is provided separately from the drive source for moving the tone arm in the vertical direction, a motor incorporated in the drive source for vertically moving the ton arm being started upon a signal emitted when the tone arm is turned horizontally to a predetermined position, and hence a peripheral cam fitted on an output shaft of the motor is rotated to cause an arm lifter to move up and down. As an alternative, there is also known a mechanism where a single drive source is employed, and driving forces are transmitted selectively to either a means for rotating the tone arm or a means for vertically moving the same, upon the switching of a clutch, and where a solenoid is used for switching the clutch.
In either case, however, the prior art has suffered many disadvantages in that two separate drive sources are required, and it is necessary to provide mechanisms for turning and for vertical movement independently from each other. The construction becomes complicated due to the need of a switching clutch, and hence the number of parts is increased.